Q.After puberty human female shows cyclic changes in her reproductive system. Explain structural and hormonal changes in the uterus.
OR
Give reasons :
(A) Scrotal sac serves as thermoregulator.
(B) Corpus luteum gets converted into corpus albicans in absence of fertilization.
(C) Missing of menses is the first indication of pregnancy.
(D) Surgical sterilization is a permanent method of birth control.
(E) Human egg is microlecithal.
You're viewing a preview — the full solution, concept, methods & PYQ mapping are locked.
Start your 14-day free trial to unlock the full solution →After ovulation, rising progesterone (with oestrogen) thickens and vascularises the endometrium (secretory phase) to prepare for implantation; without fertilization the corpus luteum degenerates, hormone levels fall...
The endometrium proliferates then becomes secretory under oestrogen/progesterone, and is shed as menstruation if implantation fails. OR: five hormonal/anatomical reasons about reproduction.
Structural and hormonal changes in the uterus (menstrual/uterine cycle): After puberty, the endometrium (the inner lining of the uterus) undergoes a repeating, roughly 28-day cycle of change driven by ovarian hormones. During the follicular phase, the developing Graafian follicle secretes rising levels of oestrogen, which stimulates the endometrium to regenerate, thicken, and develop a richer blood supply (the proliferative phase). Following ovulation (release of the egg, roughly mid-cycle), the ruptured follicle transforms into the corpus luteum, which secretes large amounts of progesterone (along with continuing oestrogen); under this hormonal influence, the endometrium becomes still thicker, highly vascular, and its glands become coiled and secretory, preparing an optimal, nutrient-rich environment for the possible implantation of a fertilized egg (the secretory/luteal phase). If fertilization and implantation do not occur, the corpus luteum has no signal (hCG) to sustain it, degenerates, and progesterone/oestrogen levels fall sharply; deprived of hormonal support, the thickened, vascular endometrial lining breaks down and is shed, along with some blood, through the vagina — menstruation — which marks the beginning of the next cycle.
OR — Give reasons:
(A) The scrotal sac serves as a thermoregulator because it holds the testes outside the main abdominal cavity, keeping them at a temperature about 2-3°C lower than core body temperature — a cooler environment that is essential for normal, healthy spermatogenesis, which fails at the higher internal body temperature.
(B) The corpus luteum is converted into the corpus albicans (a small, white, non-functional fibrous scar) in the absence of fertilization because, without the hormone hCG that a successfully implanting embryo would produce to signal and maintain it, the corpus luteum's functional life ends and it regresses into this inactive remnant.
(C) Missing of menses (amenorrhoea) is the first indication of pregnancy because a successfully implanted embryo (via its developing placental tissue) begins secreting hCG, which keeps the corpus luteum active and progesterone levels sustained, so the endometrium is retained and nourishes the embryo instead of being shed — hence the expected menstrual period does not occur. …
Unlock everything free for 14 days
- Full step-by-step solutions
- Concept-first explanations
- Methods, shortcuts & mistakes
- PYQ mapping + timed mock tests
Full access for 14 days. No credit card required.